Making fibers from molten material by extruding the melt through a plurality of nozzles (tips) or holes in a metal bushing is well known as shown in U.S. Pat. Nos. 4,740,224 and 5,244,483 for making glass fibers, the disclosures of which are hereby incorporated by reference. In these and other similar fiber making processes, the fibers frequently break for various known and unknown reasons causing breakouts of large portions of the bushing or the entire bushing. The breakouts usually start with a single fiber breaking out while the remaining hundreds to thousands of fibers from a single bushing continue to run. In a few seconds to minutes after the first fiber breaks, the bead down of that fiber will cause other fibers to break and soon many or all of the fibers will be broken out. In the event that the bushing is designed to avoid bead down during running, there is still a need to know when a certain number of fibers have broken out so that the bushing can be restarted to get all of the tips running fibers again. For evaluation and optimizing purposes it is desirable to have a record of the number and time, duration, etc. of breakouts for each bushing position.
To meet these needs, breakout detection systems have been developed. The breakout detection system (BODS) usually consists of a thermocouple mounted onto the frame of each fiberizing bushing such that the junction end of the thermocouple projects below the bushing frame and into the location where room air is pulled into the bushing tip area and fiber array by the induction created by the rapidly moving array of fibers as they are pulled downward and away from the bushing. As each fiber breaks out, less air is drawn past the thermocouple junction. After several fibers have broken out, there is enough of a temperature gain at the thermocouple junction to exceed normal temperature variation and a break is sensed and recorded.
While this system has worked very satisfactorily, the stainless thermocouple mount and Inconel protection tube required are expensive, hinder air flow, and are obstacles to bushing maintenance. Finally, the accuracy of the system can be modified by accidentally, or intentionally, moving the mount or the protection tube.